ABSTRACT
Discussions about the causes of migration, both in contemporary economies and in the past, can usually be placed into one of two categories. In one formulation the decision to migrate depends on the migrant’s expected relative income, which is the difference between the present value of an individual’s expected lifetime income if he or she migrates and the present value if he or she does not migrate, discounting for the cost of moving and for the uncertainties inherent in migration. This view of the cause of migration implies that spatial income differentials would predict migration rates.
